When adding alcohol to any dish, remove pan from flame. Add bourbon and scrape pan with a wooden spoon. Add stock and mix well removing any lumps. Bring sauce to a boil and allow to simmer for 10 minutes until sauce thickens. Add salt and pepper, if needed. Add 1 tablespoon cold butter and whisk together. Stir in reserved roast beef juice. Finish with parsley. Serve on top or along side of roasted meat.